As disclosed in U.S. Pat. Nos. 3,442,558, 3,414,337 and 3,650,579, rod guides formed of a resilient substance have long been in use to hold the rods of a sucker rod string, whose reciprocal movement in the tubing of a well actuates a pump connected in the tubing, in centralized position in the tubing. Such rod guides have a central longitudinal bore of somewhat smaller diameter than the diameter of the rods on which they are mountable in order that the guides grip the rods and tend to hold the rods with considerable force against relative longitudinal movement therebetween.
Such guides also have mounting slots having top and bottom longitudinal sections opening radially from the central bore in opposite directions and a transverse section joining the longitudinal sections so that the guides may be mounted on the rods by moving the guides onto the rods with the transverse sections of the mounting slots receiving the rods and then rotating the guides about axes perpendicular to the longitudinal axes of the rods as the longitudinal sections receive the rod, the portions of the guides on opposite sides of the longitudinal sections displacing outwardly to enable such movement of the guides until the longitudinal bores of the guides receive the rods and the guides resiliently grip the rods.
It has been found that some damage may be caused to the guides at the initiation of such rotation of the guides at the locations of contact of the surfaces of the longitudinal sections of the guide with the rods. In addition, if the end surfaces of the guides are perpendicular to their longitudinal axes, the rod guides may be expanded and forced off the rods due to the camming action of the arcuately outwardly extending surfaces of the upsets at the opposite ends of the rods if the guides are held against longitudinal movement in the tubing by engagement with an internal surface of the tubing while the rod is moved longitudinally relative thereto with a force greater than that which may cause such expansion.